fix(tools): recognize email addresses as explicit targets in send_message

When using send_message with the email platform, valid email addresses
like user@example.com were not recognized as explicit targets by
_parse_target_ref(). This caused the function to return (None, None,
False), forcing the system into channel-name resolution which has no
way to resolve a raw email address, resulting in 'No home channel set
for email' errors.

Add _EMAIL_TARGET_RE pattern and email platform handler in
_parse_target_ref() so email addresses are treated as explicit targets
and routed directly without requiring a home target configuration.

tools/send_message_tool.py

@@ -40,6 +40,10 @@ _NUMERIC_TOPIC_RE = _TELEGRAM_TOPIC_TARGET_RE
 # downstream adapters (signal, etc.) expect.
 _PHONE_PLATFORMS = frozenset({"signal", "sms", "whatsapp"})
 _E164_TARGET_RE = re.compile(r"^\s*\+(\d{7,15})\s*$")
+# Email addresses — a valid email like "user@domain.com" should be treated as
+# an explicit target for the email platform, not fall through to channel-name
+# resolution which has no way to resolve a raw address.
+_EMAIL_TARGET_RE = re.compile(r"^\s*[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,}\s*$")
 _IMAGE_EXTS = {".jpg", ".jpeg", ".png", ".webp", ".gif"}
 _VIDEO_EXTS = {".mp4", ".mov", ".avi", ".mkv", ".3gp"}
 _AUDIO_EXTS = {".ogg", ".opus", ".mp3", ".wav", ".m4a", ".flac"}
@@ -383,6 +387,10 @@ def _parse_target_ref(platform_name: str, target_ref: str):
         if target_ref.strip().isdigit():
             return f"group:{target_ref.strip()}", None, True
         return None, None, False
+    if platform_name == "email":
+        match = _EMAIL_TARGET_RE.fullmatch(target_ref)
+        if match:
+            return target_ref.strip(), None, True
     if platform_name in _PHONE_PLATFORMS:
         match = _E164_TARGET_RE.fullmatch(target_ref)
         if match: